docs: def get_legacy_fusion_langauge(identifier: ParserElement, reference: str) -> ParserElement:
      """Build a legacy fusion parser."""
      break_start = (ppc.integer | '?').setParseAction(_fusion_break_handler_wrapper(reference, start=True))
      break_end = (ppc.integer | '?').setParseAction(_fusion_break_handler_wrapper(reference, start=False))
  
      res = (
          identifier(PARTNER_5P) +
          WCW +
          fusion_tags +
          nest(
              identifier(PARTNER_3P) +
              Optional(WCW + Group(break_start)(RANGE_5P) + WCW + Group(break_end)(RANGE_3P))
          )
      )
  
      res.setParseAction(_fusion_legacy_handler)
  
      return res